Step-by-step explanation:
Work: (A)
a) 20−4x=12−x+8−3x
20−4x=12−x+8−3x
20+−4x=12+−x+8+−3x
−4x+20=(−x+−3x)+(12+8)
−4x+20=−4x+20
−4x+20=−4x+20
−4x+20+4x=−4x+20+4x
20=20
20−20=20−20
0=0
In this equation... All real #s are solutions.
Work: (B)
b) 5x+4x−3=24+8x
5x+4x−3=24+8x
5x+4x+−3=24+8x
(5x+4x)+(−3)=8x+24
9x+−3=8x+24
9x−3=8x+24
9x−3−8x=8x+24−8x
x−3=24
x−3+3=24+3
x=27
Work: (C)
c) 5x+6=2x+6+3x−15
5x+6=2x+6+3x−15
5x+6=2x+6+3x+−15
5x+6=(2x+3x)+(6+−15)
5x+6=5x+−9
5x+6=5x−9
5x+6−5x=5x−9−5x
6=−9
6−6=−9−6
0=−15
HOPE THIS HELPS <3 :D